The Symbian Foundation has launched Horizon, its application publishing programme for developers writing apps for the mobile operating system.

Horizon, which was announced in July, is designed to help developers go through the Symbian Signed application accreditation process, have their applications carried by a diversity of manufacturers' and operators' app stores, and have their applications listed in the Horizon Directory — a list of all signed Symbian apps.

Symbian Foundation chief executive Lee Williams said the organisation is aware that the diversity of application stores for Symbian increases the burden on developers by requiring multiple submission and review processes.

"But this diversity can also offer an advantage over competitors' closed systems, where applications sometimes receive arbitrary or commercially motivated rejections," Williams said. "Symbian Horizon retains this advantage, while reducing the burden by becoming a conduit to multiple stores, helping developers reach the largest global mobile market in the world more efficiently."

The Symbian Foundation announced on Tuesday that the first 50 applications had been processed, and that the programme was now fully live. Examples of the first approved apps include Facebook, the Gravity Twitter client and the Qik video-casting application.

However, those 50 applications are all for the third and fifth editions of Series 60, the current Symbian-based smartphone platform — none are for the upcoming open-sourced version of Symbian that Nokia announced in June 2008.

App compatibilityShaun Puckrin, the foundation's head of developer relations, told ZDNet UK at the Symbian Exchange & Exposition conference in London on Tuesday that application compatibility was not assured between Series 60 handsets and future handsets that would run the open-sourced Symbian. He said compatibility depended on which application programming interface (API) the developer had chosen to use.

"If it's written using [Symbian's] public APIs that are available across devices, then it will be compatible," Puckrin said. "If you use an API put in there by a manufacturer, that may cause the app to not work on Symbian 2 or 3." He gave the example of Around, an augmented reality app that runs on Series 60 5th Edition handsets that have built-in compasses, but may not work in as-yet-unreleased phones that may not have compasses.

The fact that there will not be a unified Symbian app store means that, unlike with Android, the user of a Samsung phone based on Symbian 2 or 3 will not necessarily find the same apps in their handset's app store that the user of a Sony Ericsson Symbian phone might find in theirs.

According to Puckrin, the Horizon Directory will solve that problem, letting handset users find third-party stores such as Handango, which might stock the desired application. "Hopefully that scenario is mitigated by the Directory," he said.

Asked whether the lack of a single Symbian app store with a single billing mechanism might not discourage users from buying apps on a whim, he said that "multiple stores will give people a reason to choose different devices".

In 2008, Nokia bought out its partners in Symbian and said it would completely open-source all the code in the operating system, much of which was proprietary — much of it is currently still proprietary, as only 16 of the 134 packages of code in Symbian have so far been open-sourced.

First open-source versionAt the Symbian Exchange & Exposition, Williams said the first open-source version of the operating system, Symbian 2 (S^2), was now complete, and handsets using the OS would be available in the first half of 2010.

In the first quarter of 2010, Symbian 3 (S^3) will be complete, Williams said, with handsets appearing in the second half of the year. Symbian 4 (S^4) will be complete in the third quarter of the year, with handsets appearing in the first half of 2011.

Williams said 466 new features and functionalities were currently under development for S^3 and S^4, a number he described as "stunning".

The Symbian Foundation chief also said near-field communications (NFC) would be a crucial component of the upcoming versions of Symbian. NFC is a low-powered RFID technology that is already widely used in smartcards, such as London's Oyster travelcard. It allows transactions to take place between electronic devices at very short distances.

"NFC has the ability to truly transform how mobile products and services interact with the world," Williams said, adding that the NFC capabilities being built into the Symbian platform were extensive and consistent.

Williams also said that S^3 and, to a greater extent, S^4 would have deep integration of social-networking capabilities, available to developers of all applications.